(652d) Sequential Oxidation of Glucose Using Glucose Oxidase and Au and Aupd Nanoparticles

Systems of cascade reactions are ubiquitous in biological systems using multiple enzymes to perform reactions in series. Inspired by biological cascades, we have synthesized a hybrid system that combines glucose oxidase enzyme and Au or AuPd nanoparticles for the sequential oxidation of glucose to gluconic acid and glucaric acid. Glucaric acid is one of the top value-added products that can be produced from biomass feedstocks. The glucose oxidase performs the first oxidation of glucose to gluconic acid and H₂O₂, and the Au or AuPd nanoparticles perform the second oxidation using the H₂O₂ that is produced. Au and AuPd nanoparticles are known to be selective oxidation catalysts when using H₂O₂ as an oxidant. To synthesize the AuPd nanoparticles, a new synthesis route for AuPd nanoparticles is developed in aqueous solution that does not require the use of additional surfactants or bound organic ligands. This allows the glucose oxidase to bind more effectively to the AuPd surface. Increased production of the oxidized products in the hybrid system versus the glucose oxidase and metallic nanoparticles on their own indicates cooperativity between the glucose oxidase and the metallic nanoparticles. There is a pronounced effect of pH in this system due to the glucose oxidase preferring to work at near neutral pH and the Au and AuPd nanoparticles preferring a more alkaline solution for oxidation catalysis. Changing the ratio between glucose oxidase and metallic nanoparticles leads to differences in saccharic acid selectivity. It is hypothesized that that a higher metal nanoparticle to glucose oxidase ratio leads to faster H₂O₂ decomposition on the metal nanoparticle surface and decreases the amount of H₂O₂ available for the second oxidation reaction to saccharic acid. The relationship between alloy composition and activity and selectivity to glucaric acid will also be presented.